I post it here in full for the record (and file it under the Education and Energy labels).
The "Facts" include:
What are renewable energies?
How long have renewable energies been around?
What are the advantages of renewable energies?
What the the disadvantages with renewable energies (economics related)?
What are the disadvantages with renewable energies (other)?
What does the future for renewable energies look like?
Conclusion: all comes down to economics. At the moment the cost is too high - how long will be this situation last? Probably a lot longer than most people believe.
What Are Renewable Energies?
* WHAT ARE THEY?
-- Renewable energies occur naturally and can be tapped again and again, unlike fossil fuels such as coal or oil, which take millions of years to form and can only be used once. Renewables include firewood, hydro, wind, solar, geothermal and tidal power.
-- The main renewable energy used worldwide is "biomass", mainly firewood or organic waste which is a main source of energy for more than two billion people in developing nations.
-- Biomass, which includes biofuels as a tiny fraction, accounted for about 10 percent of world primary energy use in 2004. Second was hydropower with a 2 percent share. Other major types of renewables -- wind, solar, geothermal and tidal power -- made up just one percent. By contrast, fossil fuels supply about 80 percent of world energy.
* HOW LONG HAVE THEY BEEN AROUND?
-- "Biomass is the oldest form of renewable energy exploited by mankind, mainly in the form of wood burnt to provide heat and light," the International Energy Agency (IEA) said in a review.
-- The Ancient Egyptians harnessed the wind for sailing perhaps 5,500 years ago. Windmills have operated for centuries -- from the Netherlands to Spain, where Cervantes' fictional hero Don Quixote attacked some after mistaking them for giants.
-- Hydropower turbines were first used to generate electricity in the 1880s. Hydropower has been used for hundreds of years in watermills.
-- The sun is the basis for life on earth. Bell Laboratories in the United States patented the first solar cell based on silicon in 1955 -- exploiting photovoltaics to change sunlight into electricity. Another form of solar power -- concentrating the sun's rays to provide heat -- led to solar-powered steam engines in France in the 1860s.
-- Countries such as Iceland have long exploited hot water from geothermal sources. Italian engineers were first to tap geothermal power to generate electricity in Larderello in 1904.
-- France opened what is still the world's biggest tidal power plant in 1967 at La Rance, Normandy. Water is held back by a dam at high tide and drives turbines as the tide falls.
* WHAT ARE THE ADVANTAGES?
-- Clean energies don't run out and can be tapped in many parts of the world, meaning they can help governments break dependence on imported energy.
-- Some renewable energies -- wind, solar and waves -- don't produce the greenhouse gas carbon dioxide (CO2). Others -- plant-derived fuels which are burnt such as biomass and biofuels -- only produce the same amount of CO2 that those plants originally absorbed. This is a critical advantage over fossil fuels like oil and coal for combatting climate change.
-- The U.N.'s climate panel said in a Feb. 2 report that carbon emissions from burning fossil fuels were "very likely" to be the main cause of global warming in the past 50 years.
-- Clean energies do not release other toxic pollutants associated with burning fossil fuels, and they do not have the risks or waste storage problems involved with nuclear power.
* WHAT ARE THE DISADVANTAGES?
-- Cost. Many renewable energies cannot compete without subsidies against fossil fuels, even with oil at US$60 a barrel.
-- The renewable energy lobby points out that the fossil fuel industry itself gets big subisidies and does not include the social cost of its greenhouse gas emissions.
-- Big improvements in competitiveness in recent years mean renewables are catching up with fossil fuels, with on-shore wind for example now broadly competitive.
* OTHER DISADVANTAGES:
-- The wind does not blow all the time, meaning windmills have to be backed up by other forms of electricity generation. Some people object to windmills, for instance, as eyesores.
-- Hydro power dams can cause huge disruptions -- more than one million people were forced to leave their homes by China's Three Gorges Dam, the biggest hydro project in the world.
-- The sun does not shine all day and solar power is best tapped in a "sunbelt" near the equator.
-- Geothermal power is often expensive to tap because of drilling costs.
-- Tidal power projects disrupt marine life in estuaries, only operate at falling tides and have to operate with only a few metres (yards) drop.
* WHAT IS THE OUTLOOK?
-- The IEA projects that renewables will gain overall to supply 13.7 percent of world primary energy by 2030 from 13.2 percent in 2004, in a scenario based on current trends. If governments do more to promote them, the share could rise to 16 percent.
-- The IEA reckons many renewable energies will have strong growth -- from a tiny base. But A decline in poverty would curb use of biomass as more people in developing nations get connected to electricity grids, often run on fossil fuels.
-- The European Renewable Energy Council and Greenpeace issued a 2007 report projecting half of all energy could come from renewables by 2050, with the biggest shares by then for wind and solar power followed by hydro, biomass, geothermal and ocean energy.